Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sun-barr!decwrl!shelby!neon!kanamori
From: kanamori@Neon.Stanford.EDU (Atsushi Kanamori)
Newsgroups: comp.lang.lisp
Subject: Re: Why is (read) slow?
Message-ID: <1990Oct2.211856.632@Neon.Stanford.EDU>
Date: 2 Oct 90 21:18:56 GMT
References: <20644@orstcs.CS.ORST.EDU>
Organization: Computer Science Department, Stanford University
Lines: 39

In article <20644@orstcs.CS.ORST.EDU> tgd@tesla.cs.orst.edu (Tom Dietterich) writes:
>Frequently I use large files of S-expressions as a database for moving
>information from one lisp program to another.  I find that using
>(read) to read these expressions back into lisp is extremely slow.
>If, however, I set up the file so that it can be (load)-ed instead, it
>comes in much much faster.  Have other people observed this?  Has
>anyone got an explanation?
>

Gee, you got me. Perhaps you might check up on the following theory?

  1. Whoever wrote your Lisp system hard-coded the parser into his
     "load" command without thinking about the fact that the parser
     is needed separately.

  2. Later, he realizes that Lisp also requires a "read" interface
     to the parser.

  3. Groans and slaps his head.

  4. Rather than rewrite the parser, codes up "read" as follows:

      a. Copy characters from input stream to a /tmp file.
      b. Do quick scan to find s-expression boundaries and
         edit /tmp file to change SEXPR into (setq tmpvar 'SEXPR)
      c. Calls "load" to read in /tmp file.
      d. Returns value of tmpvar.


o       o
     
    |         (a big smiley for above paragraph)
\   |   /
 \_____/



P.S.: Maybe your "load" command is secretly caching a preprocessed
version of your datafiles?